| Initial observations of the chicken immune systems led us to study the acute phase protein (APP) response. To examine the time course of an APP response in broiler chickens, the plasma levels of hemopexin (HX) and a 1-acid glycoprotein (AGP) were measured at various time points from 3 hours to 336 hours after an intra-abdominal injection of various inflammatory agents. Relative to control levels, plasma HX and AGP levels increased by 6 to 12 hours post challenge, peaked at 24 hours, and returned to control levels by 336 and 168 hours post-injection, respectively. The results suggested that plasma levels of HX or AGP could be used as an indicator of the systemic component of a local inflammatory response in chickens. To further study the chicken immune system we developed a method for the rapid separation of different leukocytes simultaneously from whole blood. Using a one-step four-layer discontinuous Percoll gradient at densities of 73% (heterophils), 63% (lymphocytes), 57% (monocytes), and 51% (thrombocytes), we separated four chicken leukocyte cell types and characterized them by flow cytometry, fluorescent microscopy, and phase contrast microscopy. Mean cell purity was 90.9% for thrombocytes, 78.5% for monocytes, 84.5% for lymphocytes, and 85.1% for heterophils. Next, we isolated C-reactive protein (CRP)-like proteins from chickens and CRP from rabbits. The isolated proteins were found at lower serum levels in lipopolysaccharide (LPS) challenged chickens (0.046 mg/ml) in comparison to (0.199 mg/ml) in LPS challenged rabbits. CRP-like proteins in the chicken were found to significantly increase the phagocytosis percentage of monocytes (P < 0.05) and heterophils (P < 0.05), but not thrombocytes (P > 0.05) over non-opsonized controls. In contrast, isolated CRP from the rabbit significantly increased (P < 0.05) the phagocytosis percentage of monocytes only, as compared to non-opsonized controls. The total phagocytosis index of chickens was significantly greater than rabbits (P < 0.05). We conclude that the greater phagocytosis index of chickens compensates for their lesser dependency on CRP-like proteins. Additionally, chickens do posses CRP-like proteins that may be major acute phase proteins (APP), which functions similarly to rabbit CRP. |
